Temporal Changes in Morphology of the Auditory and Vestibular Organs in C57BL/6J (Cdh23ahl/ahl) Mice

Abstract

Abstract C57BL/6J (Cdh23ahl/ahl) mice present with progressive hearing loss (HL) and are homozygous for the Cdh23 gene variant (c.753A), which is responsible for HL in C57BL/6J (Cdh23ahl/ahl) mice. In humans, the CDH23 gene is responsible for syndromic HL, such as congenital severe HL and bilateral vestibular dysfunction in Usher syndrome type 1D (USH1D), and non-syndromic HL, such as DFNB12, which is progressively impaired hearing at high frequencies. However, few reports have simultaneously evaluated temporal hearing function and temporal changes in the morphology of the auditory and vestibular organs. Therefore, we evaluated the transition of hearing and changes in the number of hair cells (HCs) in the cochlea and vestibule over time. Hearing thresholds gradually increased in the high-frequency range from 32 kHz to 16 kHz. At 36 weeks of age, there was also an increase in clicks and 8 kHz thresholds, which reflects the low-frequency threshold. In the cochlea, the number of inner and outer HCs (IHCs and OHCs, respectively) decreased from the basal turn to the apical turn. The number of OHCs decreased prior to that of the IHCs. The number of HCs in the utricles remained unchanged until 60 weeks of age. Our results demonstrate that C57BL/6J (Cdh23ahl/ahl) mice present with DFNB12 features rather than USH1D features.